The normal control over the passage of urine is thought to be achieved by two mechanisms. One such mechanism involves the sphincter muscular action which affects the lower part of the tubular outlet of the bladder normally to provide a steady tonic contraction at rest and an increased contraction during coughing. lifting or other stress when the pressure in the abdominal cavity rises. The second mechanism involves the transmission of abdominal pressure to the proximal part of the outlet of the bladder, the urethra, enabling the pressure acting on the urethra from without the same to rise correspondingly with that acting on the urethra from within by way of the bladder when stressed.
This second mechanism requires that the upper part of the urethra be located within the abdominal pressure zone and, in women, this is above the muscles of the floor of the pelvis. It follows that loss of this mechanism is commonly associated with prolapse such that the female urethra is lowered from the pressure zone, with a consequent incidence of stress incontinence.
Different proposals have been made for treatment of this last condition, but none appears fully satisfactory.
Surgical treatment normally involves elevation of the base of the bladder to restore a normal location for the urethra. Commonly performed operations are urethroplasty, in which the urethra is buttressed from below, and coposuspension, in which structures surrounding the urethra are sutured to ligaments above it in the pelvis. Another deploys a sling construction. All of them can lead to urethral scarring which may adversely affect normal function.
A subsequently proposed treatment involves the use of a pedicle graft of fat taken from an adjacent site and placed wholly or partly as a cuff around the urethra to restore its mobility and flexibility. Unfortunately the fat tends to disappear with time.
Other treatments involve the use of mechanical aids, such as a hydraulically inflatable urethral cuff or a vaginal inflatable pessary, or synthetic materials such as polyethylene gauze, but these can prove unsatisfactory by way of mechanical failure, discomfort, foreign body reaction, and other eventualities.